Wellbores drilled through the Earth's subsurface may be oriented in various directions and as such, may be vertical, deviated or horizontal wellbores. A multilateral well may have a parent wellbore and one or more lateral wellbore branches, which extend from the parent wellbore into the surrounding formation. The parent wellbore may be cased by a casing string that lines and supports the parent wellbore. Liners may line and support the lateral wellbores that extend from the parent wellbore. The casing and possibly the liners may be cemented in place in the well.
A lateral wellbore of a multilateral well may be completed after the main parent wellbore has been drilled and cased. In this manner, the lateral wellbore may be formed by running a drill string into the parent wellbore; extending the drill string through a milled or preformed opening called a “casing window” of the parent casing string; and drilling the surrounding formation. For such purposes as deflecting mills into the parent casing wall to form the casing window and guiding a drill string in the appropriate direction to form the lateral wellbore, a tool called a “whipstock” may be deployed in the parent wellbore. In this regard, the whipstock may be anchored in place in the parent wellbore below the location of the casing window so that an inclined surface of the whipstock may be used for purposes of guiding the mills and the drill string.